A Chinese study reveals people who smoke could be more likely to develop type 2 diabetes.

The international team behind the research were unable to conclude that smoking causes type 2 diabetes, but stress that smoking should be considered an "important modifiable lifestyle factor" in tackling diabetes rates.

Researchers from the University of Oxford, UK, the Chinese Academy of Medical Sciences and Peking University examined smoking risk in 500,000 adults within urban and rural areas of China. None of the participants had type 2 diabetes before the review.

The participants were followed for nine years with health records taken from death and hospital admission records. During this time more than 13,500 of the cohort developed type 2 diabetes.

Compared with those who never smoked, regular smokers were 15-30% more likely to develop type 2 diabetes once confounding variables such as age and alcohol consumption were taken into account.

The findings also revealed a dose-response relationship, indicating those who smoked more had a greater likelihood of type 2 risk, while those who started smoking at an earlier age were also at greater risk.

There were particularly interesting findings regarding smoking and weight. Those who smoked and had a concurrently high BMI were most likely to develop type 2 diabetes compared with smokers who had a lower BMI. Interestingly though smokers tended to be leaner, on average, compared to non-smokers, with the researchers suggesting this could be attributable to smoking suppressing appetite. Additionally, heavy smokers were more likely to have greater abdominal fat compared to light or non-smokers, which further raises type 2 diabetes risk.

Excess diabetes risk remained in recent quitters who had stopped smoking due to illness, but fell among those who stopped smoking for other reasons.